Testing for pregnancy should be done at the end of your cycle. If you're irregular I would suggest waiting until after the 30 th day of your cycle. Sometimes it may not show up right away. But how long after you have sex has nothing to do with testing time. It's where you are in your cycle that matters. If you have a hard time keeping track of it, mark the dates on a calendar. Are you trying to get pregnant or afraid that you might be?